Pneumonia, Meningitis and Sepsis | Action Medical Research | Children's Charity | Children's Charity

Pneumonia, meningitis and sepsis: when harmless bacteria become deadly

First published on 18 February 2010

Updated on 7 October 2013

What did the project achieve?

Researchers led by Professor Chris O’Callaghan have made a breakthrough in the fight against pneumonia, meningitis and sepsis. They have discovered why a bacterium called the pneumococcus, which is normally quite harmless, may suddenly become deadly, causing these life-threatening infections.

Many people carry pneumoccocal bacteria in their nose and throat without suffering any ill effects. Yet estimates suggest over 1.5 million people worldwide die each year from infections caused by these bacteria.1 Many are children less than five years old.1

“Pneumococcal infection is the commonest cause of severe pneumonia and one of the commonest causes of severe meningitis worldwide,” says Professor O’Callaghan.2,3 “Before starting this work, we already knew that infection with a virus, called the respiratory syncytial virus or RSV, puts children at increased risk of serious pneumococcal infections. The reasons for this were unknown.”

The team’s discoveries help explain this mystery: “We have uncovered how infection with RSV may cause pneumococcal bacteria to become much more dangerous,” says Professor O’Callaghan.

These important findings could lead to new treatments and the team is currently investigating how new treatments against RSV might work. The ultimate aim is to prevent infections, hopefully saving children’s lives and reducing their suffering.

This research was completed on 31 August 2012

The pneumococcus can be a deadly bacterium, causing pneumonia, meningitis and sepsis. Up to one million children under five lose their lives to diseases caused by this bacterium each year worldwide.1 Yet many healthy people carry pneumococcal bacteria in their nose and throat without suffering any ill effects. Researchers are investigating why this normally harmless bacterium sometimes becomes deadly. They hope their work will ultimately save lives and prevent disability, by leading to new ways to beat infection.

What's the problem and who does it affect?

Harmless or deadly?

The World Health Organisation estimates that over one and a half million people worldwide die each year from serious infections like pneumonia, sepsis and meningitis caused by a bacterium called the pneumococcus.1 Many of those who lose their lives are children less than five years old.1

Antibiotics can kill the pneumococcus. Tragically however, many children die even if they are treated and those who survive can be left with lifelong disabilities. Children who battle through meningitis, for example, can go on to develop learning disabilities, vision or hearing loss, seizures and behavioural problems.

Strangely, though pneumococcal bacteria can be so dangerous, many healthy people carry them in their nose and throat without suffering any ill effect. So what makes these normally harmless bacteria suddenly turn nasty and cause devastating infections like meningitis? No-one knows for sure, but evidence suggests viral infections may be involved. With so many children’s lives at stake, it is essential to find out more.

What is the project trying to achieve?

Changing danger levels

The researchers are investigating why pneumococcal bacteria, which are normally quite harmless, can sometimes become so deadly.

Evidence suggests that people who have suffered certain viral infections are more susceptible to severe pneumococcal infections like pneumonia, meningitis and sepsis. One virus that seems to put people at increased risk is called RSV. It has recently been estimated that RSV-associated lower respiratory tract infections cause the death of up to 199,000 children under the age of 5 years, each year, with the vast majority of deaths occurring in developing countries.2

The researchers working on this project recently discovered that some viruses seem to make pneumococcal bacteria more toxic. They also found out that RSV causes pneumococcal bacteria to stick to the lining of the lungs in clumps.

In this project, the researchers are investigating their discoveries in detail, by infecting human cells donated by volunteers, to find out more about how RSV makes pneumococcal bacteria more dangerous.

What are the researchers' credentials?

Project LeaderProfessor C O'Callaghan PhD FRCP FRCPCH
Project team
  • Professor Peter Andrew PhD
  • Professor Andrew Easton PhD
LocationDepartment of Infection, Immunity and Inflammation, University of Leicester, Leicester Royal Infirmary in conjunction with Department of Biological Sciences, University of Warwick, Coventry
Other locations
  • Department of Biological Sciences, University of Warwick
Duration2 years
Grant awarded18 November 2009
Start date1 January 2010
End date31 August 2012
Grant amount£119,218.00
Grant codeSP4499

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Three researchers with internationally recognised expertise are collaborating on this research. The project leader, Professor Chris O’Callaghan, is a specialist in respiratory medicine and an expert on cilia – tiny hair-like structures in the lining of the lungs on which pneumococcal bacteria can grow. He is working with Professor Peter Andrew, a leader on research into pneumococcal infection, and Professor Andrew Easton, a leading authority on RSV infections.

Over the last two years, the project team has developed sophisticated laboratory techniques that will be invaluable in their investigation into why viruses can predispose people to severe bacterial infections.

Who stands to benefit from this research and how?

Hopes of saving children’s lives

The researchers hope to reveal how viral infections put children, and adults, at increased risk of developing life-threatening bacterial infections like pneumonia, meningitis and sepsis. They hope to explain why pneumococcal bacteria, which are normally quite harmless, can suddenly become deadly.

The researchers believe their work could eventually help save children’s lives and spare them from disability, by leading to new ways to combat pneumococcal infections. Diseases caused by this bacterium are a major public health problem worldwide.1 As well as causing life-threatening illnesses, infection can lead to more common but less serious problems such as middle ear infections, sinusitis and bronchitis.

Pneumococcal infections kill an estimated 1.6 million people each year – with many being children less than five years old.1 Those who survive their infection can be left with lifelong disabilities. Large numbers of people around the world – mostly very young children – could therefore benefit greatly from this important research.


  1.  World Health Organisation (WHO). Pneumococcal conjugate vaccine for childhood immunization – WHO position paper. Weekly epidemiological record 23 March 2007, 82 (10):93-104.
  2. Global burden of acute lower respiratory tract infections due to respiratory syncytial virus in young children: a systematic review and meta-analysis.  Lancet: 2010; Published online April 16.
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